[asterisk-bugs] [Asterisk 0017091]: T.38 faxmaxdatagram overflows with UDPFEC, works with "t38pt_udptl=yes, redundancy" (udptl.c)

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=17091 
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Reported By:                rlr2maverick
Assigned To:                
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Project:                    Asterisk
Issue ID:                   17091
Category:                   Channels/chan_sip/T.38
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     feedback
Asterisk Version:           1.6.1.18 
JIRA:                       SWP-1169 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2010-03-24 09:36 CDT
Last Modified:              2010-03-24 10:47 CDT
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Summary:                    T.38 faxmaxdatagram overflows with UDPFEC, works
with "t38pt_udptl=yes,redundancy" (udptl.c)
Description: 
Our 1.6.1.18 works with any sort of fax call using standard ReceiveFax and
SendFax provided by appfax, only after changing UDPFEC default parameter
which causes a buffer overflow with faxmaxdatagram (properly negotiated as
per 180 among ATA and Cisco 3825).

The environment consist of:

       FAX <-> ATA <-> ASTERISK <-> ROUTER 3825 <-> PSTN (audio fax)
               ^^^                         ^^^
faxmaxdatagram=180          faxmaxdatagram=180

SIP debug shows faxmaxdatagram properly negotiated but following ECM
packets are  discarded by 3825 causing either fax call to abort
prematurely, packets encoded with UDPFEC overflow the maximum admitted
size.

changing udpfec (default) with "t38pt_udptl=yes,redundancy" we got near
100% fax send/receive success.  
    
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 (0119818) rlr2maverick (reporter) - 2010-03-24 10:47
 https://issues.asterisk.org/view.php?id=17091#c119818 
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udptl.c related problem confirmed !!! (as per my recent additional
information). I found lot of " ... Buffer overflow detected ... " in full
logfile. The only code where it could lie is udptl.c line 302

[Mar 18 17:27:05] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (77 + 170 > 180)
[Mar 18 17:27:05] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (77 + 170 > 180)
[Mar 18 17:27:05] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (77 + 170 > 180)
[Mar 18 17:27:05] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (77 + 170 > 180)
[Mar 18 17:27:05] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (77 + 170 > 180)
[Mar 18 17:27:05] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (77 + 104 > 180)
[Mar 18 17:27:13] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (65 + 146 > 180)
[Mar 18 17:27:13] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (65 + 146 > 180)
[Mar 18 17:27:13] ERROR[12132] udptl.c: (SIP/00243828330): Buffer overflow
detected (65 + 146 > 180) 

Issue History 
Date Modified    Username       Field                    Change               
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2010-03-24 10:47 rlr2maverick   Note Added: 0119818                          
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